1. Field of the Invention
The present invention relates to (i) a laser spark plug equipped to be installed in a plug shaft of an internal combustion engine, (ii) a cooler for such a laser spark plug, and (iii) a laser ignition device.
2. Description of the Related Art
Such a laser spark plug, such a cooler and such a laser ignition device are known in each case from published European patent application document EP 1 519 038 A1. In the subject matter of published European patent application document EP 1 519 038 A1, the actual laser spark plug, which, among other things, has a pumped solid laser as the ignition laser, a pulsed pump light source, a resonator and an output mirror, is integrated together with a cooling device into a single component that is able to be inserted into a plug shaft of the internal combustion engine.
The single component is also designated as laser ignition device in published European patent application document EP 1 519 038 A1. This laser ignition device has a base near the combustion chamber and a headpiece. The headpiece is situated at the end of the laser ignition device, which lies opposite the base, and thus represents the end that is at a distance from the combustion chamber. The direction, in which the headpiece is separated from the base by a distance, defines the direction of the longitudinal axis of the component. In the headpiece, essential components of the laser spark plug are combined, such as the pump source and the ignition laser, with the cooler, which has a Peltier element and elements of a liquid cooler. In this context, the ignition laser is situated centrally near the longitudinal axis of the laser ignition device, the pump sources are situated concentrically about the ignition laser. Cooling channels of the fluid cooler are situated further out at the same height, that is, at about the same distance from the base as the pump source and the ignition laser. The headpiece and the base are connected to each other via an extended and slender tube. The headpiece extends beyond the tube in the radial direction. According to one figure of published European patent application document EP 1 519 038 A1, the headpiece also extends out of the plug shaft in the direction of the longitudinal axis, and in the radial direction it extends beyond the diameter of the plug shaft.
Because of the situation of the laser components in the headpiece, there comes about a large, if not even maximally large distance between the laser components and the output mirror. This is designated in published European patent application document EP 1 519 038 A1 as being an essential feature for achieving a high radiation quality.